jacobson



Dec. 17', 1957 D. A. JACOBSON Re. 24,405

GAS FUELEDV RADIANT HEATER Original Filed Oct. 6. 1950 2 Sh oots-Sheat 2 QII/ i'lllllllll |||||I||l||||| Fly. 5 17 2 INVENTOR.

Dona/a J. Jacobson Arrokusy United States PatentOfiice Patented Dec. 17, 1957 GAS FUELED RADIANT HEATER Donald A. Jacobson, Grand Rapids, Mich., assignor to Granco, Inc., Grand Rapids, Mich., a corporation of Michigan Original No. 2,649,907, dated August 25, 1953, Serial No. 188,692, October 6, 1950. Application for reissue April 18, 1955, Serial No. 502,261

12 Claims. (Cl. 158-113) Matter enclosed in heavy brackets appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

The present invention provides a gas-fired generator of radiant heat energy. A gas flame is directed upon a ceramic target, to maintain it [as] at such a temperature as to generate as much heat energy as is possible in the form of infra-red rays and radiation of similar wave length. Such devices also dissipate a considerable amount of the heat provided by the gas in the form of heated air; and in general, the measure of their value is the percentage of heat energy provided by the fuel that is realized in the form of radiant heat. These units are used in industry in drying operations, in the heat treatment of various metals, and wherever it is necessary to create an elevated temperature. It is a Well known and valuable characteristic of infra-red radiation that it possesses great power of penetration rather than concentrating the heating efiect upon the surface of a material, as would be the case if it were to be subjected to merely a draft of heated air.

Radiating targets maintained at elevated temperatures by gas flames (or by the use of other fuel) are well known. One widely used form of this device involves a highly porous block of ceramic material through which fuel gas is urged under pressure. Ignition takes place at the surface of the block, and the radiation from the flame back on to the ceramic material raises the temperature of the material enough to cause radiation of heat energy at the desired wave length. Another type of device involves an annular or linearly-disposed trough, with a jet of fuel gas directed downwardly along one edge of the trough. Combustion takes place during the passage of the gas across the concave surface of the trough, and the temperature of the burning gases cause the required elevation in temperature of the ceramic material to generate the radiant heat energy. It may be noted in regard to this type of device that the concave configura- Lion of the trough has the effect of focusing the radiation so that a lack of uniformity in intensity over any substantial area results. The principal objection to both of the general types of devices known to the prior art is the relatively high percentage of available heat in the incoming fuel gas that is wasted in the heating of the surrounding air, with the consequent reduction in the percentage of heat energy that is made available in the form of radiant energy. Another objection is the diffi- :ulty that is encountered in turning down" these units to 1 low fuel consumption. It is advantageous to be able to ldjLlSt a given unit for varying the heating intensity as 'equired.

The present invention provides a heating unit of the :eramic target type in which the target is formed with 1 series of parallel channels for the passage of the burnng fuel gas. These channels are best arranged vertically 1nd curved at the base so as to force the burning prodlcts of combustion to thoroughly scour the surface of the arg'et to create the maximum transfer of heat. With he burning fuel thus confined within relatively narrow channels in the ceramic material, the best possible transfer of heat energy from the products of combustion to the target is achieved. As a consequence of this feature, the fuel gas is impinged upon high temperature surfaces substantially throughout the entire mass of the jet of gas in contrast to the old arrangement in which only a boundary portion of the jet impinges upon the heated surface. The latter case results in relatively gradual elevation of the temperature of the fuel to the point of ignition. Such gradual burning has a tendency to result in incomplete combustion within the area of the target where the heat can be utilized to generate radiant energy.

A fuel-distributing chamber for controlling the emission of fuel gas is provided by the present invention, and a jet of gas is established by a slot in the wall of the chamber so positioned that the jet impinges upon the back wall of another slot at the fuel receiving ends of the channels and then upon the lower-most portion of the channels in the ceramic target. This jet is kept extremely thin so as to permit immediate elevation of the fuel gas to the temperature required for combustion. With this arrangement, the fuel gas begins ignition at approximately the point of entry of the combustion channels, with the elevated temperature of the ceramic material hastening and completing the process of combustion within the confines of those channels. Suitable baffles are provided within the chamber to assure a uniform density and velocity of the jet of fuel along the length of the slot.

The disposition of the fuel-distributing chamber (preferably formed of metal) with respect to the heated ceramic target is such as to place a small portion of the chamber within the space defined by the normally (perpendicularly) projected area from the radiating face.-

This arrangement results in pre-heating the fuel gases to a point where the temperature of combustion can take place at a very short distance beyond the slot from which the fuel gases emerge. The slot is also positioned so that the chamber extends on both sides of it, so that a portion of the fuel is permitted to traverse the heated area of the chamber before emerging from the slot. The relative position of the target and the chamber is maintained by an extremely simple assembly system in which the mounting of the target is secured by a simple screwfastened clip.

The various features of the present invention will be analyzed in detail through a discussion of the particular embodiments illustrated in the accompanying drawings. In these drawings:

Figure 1 is a perspective view showing an installation of a series of units constructed according to the present invention in a drying oven.

Figure 2 is a perspective view showing an assembled heating unit attached to a fuel-supply conduit.

Figure 3 is a section taken through the assembled unit.

Figure 4 is a section taken on the plane 4-4 of Figure 3.

Figure 5 is a. section taken on the plane 5-5 of Figure 3.

Figure 6 is a perspective view showing the attaching clip holding the target and fuel-distributing chamber in screened by 999K929! the are: ellm through the aperture 13. w

A series of heating units. is indicated at 14 and is a ran ed sma th a ns par ies Qtth area Each of hese h tin ai i mount d u n a h r e t of r pe se u ly at ached 0th? ta p nduit 5 e direction of radiation from the heating units forming he Se i s. 1 h t t e W r -P ce 2, are subtes ed o d a hea ur n their passag down. the oxe 10.-

Ref rin Q F gure 2 th ou h inclusive, the series of heating units 14 made up, by the individual units as s hgwn in Figure 2. The short vertical length of pipe 1a s as q ted w th the m in supp y nd 15 a d pports the fuel-distribution chamber 17-. The interior construction of this chamber is such as to create a uniform flow of gas out through the slot 18. throughout its entire length. The construction of the chamber to accomplish this may be considered to, include the exterior. walls 19, 20 nd A bottom 22 together with the upper flat surface 23, and the arcuate surface 24 complete the chamber provided by the manifold. A portion 25 ex; t e ds throughout the length of the chamber, and the battle partitions 26 provide a series of channels tending to remove any flow of gas along the length of the chamber within that portion of the unit. These bafile partitions serve to maintain an even distribution of gas along the length of the slot 18. Fuel gas entering through the supply conduit 15 passes through the short pipe 16 and enters the portion of the chamber 25. The partitions 26 guide the flow of fuel, and the fuel passes between them to the slot 18 acting as an exit orifice.

The fuel gas emerging at the slot 18 passes over a short table-like surface 27. The temperature of this surface is low enough to inhibit the flashback that might take place if the surrounding temperature were elevated to the point of combustion. After the fiow of gas passes beyond the surface 27, it impinges upon the ceramic target 28. At this point, the ribbon of fuel gas emerging from the long slit or slot 18 is divided into a series of channels provided by the slots 29 defined by the Efaces] flanges 29a projecting from the curved wall 39a of the target 28. The target is provided with a slot 40 at the bltse of the channels 29 directly opposite the fuel discharge slot 18. The fuel receiving ends of the channels 29 communicate with the slot 40. The flanges 29c have terminal edges forming the surfaces and 31. The curved wall 30a has an upper terminal end 41 at its top and a lower terminal end 42 at the hereinafter identified slot 46. When the stream has emerged from the surface 30, the process of combustion will have been completed. During the passage of the gases through the channels 29, the heat contained in the products of combustion will be transferred in a large degree to the target so as to raise the temperature thereof to a point where radiation of heat energy takes place from the surfaces 30 and 31. It will be noted that the upper curved surface 24 of the manifold is placed Within the space defined by the normal projection of the surface 31. This feature facilitates elevating the temperature of the manifold to a point where the fuel gases are preheated to such a degree that combustion takes place at the desired point in transit from the slot 18 over to the target 28.

Referring to Figure 7, the paths of fuel gases and secondary air are substantially as indicated by the curved lines, with the direction of flow noted by the arrows. The fuel gas entering from the pipe 16 passes along the general line 32. This path of fuel may have a cornpcnent along the chamber portion 25, and will pass hrou h we at he 911 .1 e fs define y the Psrt ii h ft! 1 n he i e is is m xed. w t prepay quail r e sslflis sat is swee 991Pi ch The high ci at wh the ass emer s thre sh the slot 18 induces a flow of secondary air along the line 3.3,, this flow, being facilitated .by. the curvature of the surface 24. The fuel and primary air becomes intermixed with the secondary air during transit across from the slot 18 to the target 28, and continues the process of mixture through the early stages in which the gases pass through thefchannels 29. Combustion preferably begins at approximately the point of juncture of the lines 33 Qas'indicated in Figure '7.

The arrows 34 indicate the general direction of the maximum radiation of heat energy from the surface 3Q, and the arrows 35 from the surface 31. I These surfaces are actually not continuous, and form the fronts of the partitions or fins between the channels 29.

When a combustible mixture of air and gas delivered at a pressure above atmospheric is burned, the flame will assume a widened pattern. Some of this is; due to the further mixing with th e n irrgcs mixture of sccond ry air creating a combustible mixture on the periphery. of. the flame pattern. It is, however, largely due to theexpansion of the gases as their temperature rises. his expansion must be expressed as either an increase in velocity, i. c., expansion, in the direction of flow of the ui-r-gg s mixture or as lateral expansion, i. e., widening of the gas envelope. The greater part of this expansion occurs. laterally because this is normally the path of least resistance, and, sharp increases in velocity will result in extinction of the flame since combustion normally can occult only n. a very limited range of critical velocities. If this range is exceeded, flame blow out occurs. This lateral spread in flame pattern will occur even though combustion is carried out. in a non-confined area.

When combustion occurs in a zone where either the gas. forward.- expansion or its lateral expansion or both is partially restricted, the flame pattern will tend to. concentrate its expansion in the direction of least resistance. Thus, in the present invention, the flame pattern will expand in the flame channels 29 in a direction normal to, curved surface 30a of the target.

While the degree of curvature of the surface 30:: or its inclination to the direction of the jet of air-gas 'mixture discharged from the slit 18 will, to some extent, aflect the height to which the flame pattern will extendnormal to the surface 30a, this flame height maybc calculated mathematically, provided it is assumed that all combustion is. to be confined to a zone in which lateral expansion is. limited to, one direction and the s ides of the zone rise at least to the height of the flame.

The assembled relationship of the target 28 and the chamber is maintained by the engagement of the projection 36. on the target 28 with the corresponding recess in the metal casting forming the chamber 17' in tongueand-groove relationship. The target 23 is held in engage ment in this manner by. the action of the clip 37 secured to the casting by the screw 38; The target can be removed from the assembly by the removal of the screw 38-. The clip 37- is adapted to receive the screw at the slot 39. provided to permit vertical adjustment, to allow for manufacturing tolerances and properly, posi} tioning the target 28 with respect to the slot 18 and the tablesurface 2'7.

The particular embodiments which have been illustrated in the accompanying drawings and discussed herein are.

for illustrative purposes only and are not to be considered as limitations upon the scope of the appended claims. i H l I claim:

1 gas burner comprising a fuel distributing member having a peripheral wall defining an elongated passage containing an inlet port, transverse walls integral with said member defining fwith said peripheral wall a plurality. of compartments adjacent said passage and communicat- 15. n an -11 air ptt 'r re il av mm n d?! and containing a continuous narrow slot;

er,secti ng said compartments. generating radiant heat comprising fuel discharge means containing a delivery slit, flame target means including a member having a curved wall concavely disposed towards said slit and terminating adjacent said slit, and a plurality of parallel spaced flanges projecting from said wall and defining flame passages therebetween to receive gas from said slit, said flanges terminating in substantially a plane, whereby gas delivered from said slit enters said passages and follows a curved path and heat is radiated from said flanges at said plane] 3. A gas burner for generating radiant heat comprising: fuel discharge means containing a delivery slit, flame target means including a member having a curved wall concavely disposed towards said slit and terminating adjacent said slit, and a plurality of parallel spaced flanges projecting from said wall and defining flame passages therebe tween to receive gas from said slit; said target having a slot parallel and opposite to said slit; said slot communicating with said flame passages; said flanges terminating in substantially a plane whereby fuel delivered from said slit enters said slot and then said flame passages and follows a curved path and heat is radiated from said flanges at said plane.

4. A gas burner for generating radiant heat comprising: fuel discharge means containing a delivery slit, flame target means including a member having a curved wall concavely disposed towards said slit and terminating adjacent said slit, and a plurality of parallel spaced flanges projecting from said wall and defining flame passages therebetween to receive gas from said slit; said target having a slot parallel and opposite to said slit; said flame passages communicating at their fuel receiving ends with said slot; said flanges terminating in substantially a plane whereby fuel delivered from said slit enters said slot and then said flame passages and follows a curved path and heat is radiated from said flanges at said plane.

5. A gas burner for generating radiant heat comprising: fuel discharge means containing a delivery slit, flame target means including a member having a wall inclined away from said slit disposed towards said slit and terminating adjacent said slit, and a plurality of parallel spaced flanges projecting from said wall and defining flame passages therebetween to receive gas from said slit; said target having a slot parallel and opposite to said slit; said slot communicating with said flame passages; said flanges terminating in substantially a plane whereby fuel delivered from said slit enters said slot and then said flame passages and follows an inclined path and heat is radiated from said flanges at said plane.

6. A gas burner for generating radiant heat comprising: fuel discharge means containing a delivery slit, flame target means including a member having a curved wall concavely disposed towards said slit and terminating adjacent said slit, and a plurality of parallel spaced flanges projecting from said wall and defining flame passages therebetween to receive gas from said slit; said target having an ignition slot parallel and opposite to said slit at the inner end of said flanges, said slot communicating with said flame passages; said slot being adapted to eflect ignition of fuel as said fuel enters said flame passages; said flanges terminating in substantially a plane whereby fuel delivered from said slit enters said slot and then said flame passages and follows a curved path and heat is radiated from said flanges at said plane.

7. A gas burner for generating radiant heat comprising: fuel discharge means containing a delivery slit, flame target means including a member having a wall inclined to the plane of said slit disposed towards said slit and terminating adjacent said slit, and a plurality of parallel spaced flanges projecting from said wall and defining flame passages therebetween to receive gas from said slit; said target having a slot parallel and opposite to said slit at the inner ends of said flanges; the fuel receiving ends of said flame passages communicating with said slot; said flanges terminating generally in a plane angularly disposed to the plane of said slit whereby fuel delivered from said slit enters said slot and then said flame passages and heat is radiated from said flanges at said plane.

8. A gas burner for generating radiant heat comprising: fuel discharge means containing a delivery slit, flame target means including a member having a wall inclined away from said slit and terminating adjacent said slit, and a piuralityof parallel spaced flanges projecting from said wall and defining flame passages therebetween to receive gas from said slit; said target having a slot parallel and opposite to said slit located at inner ends of 'said flanges; said slot communicating with said flame passages; said flanges terminating in substantially a plane angularly disposed to said slit whereby fuel delivered from said slit enters said slot and then said flame passages and heat is radiated from said flanges at said plane.

9. A gas burner for generating radiant heat comprising: fuel discharge means containing an elongated delivery slit, flame target means including a member having a plurality of parallel spaced flanges defining a plurality of flame passages open toward said slit and closed away therefrom; said target having a slot parallel and opposite to said slit and adapted to receive fuel from said slit; said slot communicating with said flame passages; said flanges terminating in a plane disposed generally at an angle to the plane of said slit whereby fuel delivered from said slit enters said slot and then said flame passages and heat is radiated from said flanges at said plane.

10. In a gas burner for generating radiant heat, comprising: fuel discharge means having a delivery slit; flame target means including a member having a plurality of parallel spaced flanges defining flame passages therebetween; said target having a slot parallel and opposite to said slit at the inner sides of said flanges and adapted to receive fuel discharged by said slit; the fuel receiving ends of said flame passages communicating with said slot.

11. In a gas burner for generating radiant heat, comprising: fuel discharge means having a delivery slit; flame target means including a member having a plurality of parallel spaced flanges defining flame passages therebetween; said target having a slot parallel and opposite to said slit and adapted to receive fuel discharged by said slit at the inner sides of said flanges; said slot communicating with one end of each of said flame passages.

12. In a gas burner for generating radiant heat, comprising: fuel discharge means having a delivery slit; flame target means including a member having a plurality of parallel spaced flanges defining flame passages therebetween; said target having an ignition slot parallel and opposite to said slit; said slot communicating with one end of each of said flame passages; said slot being adapted to receive fuel discharged from said slit and to effect ignition of said fuel as said fuel enters said flame passages.

13. Structure as in claim 11, said slot and flame passages having closed backs provided by said flame target, and said flame passages progressively increasing in depth away from said slot.

References Cited in the file of this patent or the original patent UNITED STATES PATENTS 1,704,875 Vaughn Mar. 12, 1929 2,410,542 Kemp Nov. 5, 1946 2,464,333 McGlaughlin Mar. 15, 1949 2,533,143 Scarbau Dec. 5, 1950 FOREIGN PATENTS 13,595 Great Britain of 1915 

